Blockage or no blockage, take heart attacks seriously

The women has heart disease and go to hospital urgent. People with heart problem concept

For years, people who suffered heart attacks but didn’t have major blockages in their arteries — a condition called myocardial infarction with nonobstructive coronary arteries (MINOCA) — were thought to have a less serious form of heart disease. As a result, doctors often opted against aggressive follow-up treatments. But a study published June 15 in the International Journal of Cardiology contributes to the growing body of evidence that MINOCAs merit follow-up treatment.

The study, which looked at data from an online Swedish cardiac registry, found that a quarter of people who were diagnosed with MINOCAs went on to have another major cardiovascular event, such as another heart attack, a stroke, or heart failure. Of the original group of 9,092 people who were diagnosed with MINOCAs (62% of them women), some 2,147 went on to have another cardiovascular event during a follow-up period averaging about 4.5 years.

“What’s been seen is that these people have recurrent heart attacks, and that’s one of the findings in this study,” says Dr. Christopher Cannon, cardiologist at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School. “That says we need to be sure that we don’t just say ‘You have nothing serious,’ but instead, pay close attention and give these patients the same treatments as other heart patients.”

Different heart attacks, different findings

Most heart attacks happen when a blockage in an artery cuts off blood supply to part of the heart muscle, causing damage. “The classic case is that an artery is 100% blocked off, the person suffers crushing chest pain, we take him or her to the catheterization lab and open up the artery and restore blood flow,” says Dr. Cannon. In other people, the artery may be 85% or 90% blocked, and the same procedure is performed — but on a nonemergency basis.

However, in a small subset of people — an estimated 5% — doctors find all the other clinical signs of a heart attack, but only a small amount of buildup in the arteries — a blockage of 50% or less. Sometimes there is no blockage at all. “The person may have chest pain and comes in for a test, and we find heart damage, but we don’t find any real blockage there.”

It becomes something of a mystery as to what caused the heart attack. For this reason, some doctors have come to treat a MINOCA almost as if it were a false positive, not a true heart attack, according to the American College of Cardiology (ACC).

What’s in a name?

It wasn’t too long ago that MINOCAs didn’t even have a name, says Dr. Cannon. Cardiologists have been aware of this condition for the past 75 years, according to the ACC. But it wasn’t a diagnosis, just more of an oddity. “A MINOCA is something that we would see but not necessarily label,” says Dr. Cannon. Getting an official name in 2012 has boosted the condition’s profile and garnered it some added attention, he says. Even so, MINOCA is still not a final diagnosis but a working diagnosis, a starting point for doctors to determine what actually led to the heart attack. This is the case because a MINOCA is probably not caused by one problem — but rather by different factors in different people. These include the following:

Abnormalities in the arteries. Some cases of MINOCA may be caused by a spasm in the artery, says Dr. Cannon. Studies have found that the arteries in patients who experience a MINOCA behave abnormally in response to elevated blood pressure. In healthy people, the arteries normally open up when blood pressure rises. But the arteries of some people with coronary disease constrict under pressure, which may lead to a heart attack.

Blood clots. Other MINOCAs may be triggered by tiny blood clots that break loose and cause a blockage, but dissolve by the time the patient is examined, says Dr. Cannon.

Underlying heart problems. Additional conditions that have been linked to MINOCAs include inflammation of the arteries or of the heart muscle.

While there may be different factors that lead to MINOCAs, the study was able to identify risk factors that make it more likely that a person who experiences a MINOCA will go on to have another cardiac event.

These include many of the same risk factors seen in people who’ve suffered a more traditional heart attack with a blockage: older age, high blood pressure, diabetes, a history of smoking, a previous heart attack or stroke, chronic obstructive pulmonary disease, peripheral vascular disease, dementia, or a personal history of cancer, among others.

Treating MINOCAs

While researchers are currently trying to solve some of the mysteries surrounding MINOCAs, Dr. Cannon says doctors should treat someone with a MINOCA as they would any patient who’s had a conventional heart attack caused by a blockage.

This includes prescribing the same medications: antiplatelet agents such as aspirin or clopidogrel (Plavix) or anticoagulants (blood thinners) to discourage clotting, drugs to reduce blood pressure, and statins to lower blood cholesterol levels, says Dr. Cannon. In addition, people who’ve had a MINOCA should also be closely monitored for elevated blood pressure and diabetes and encouraged to make lifestyle changes, such as exercising, eating a healthy diet, and quitting smoking.

“Sometimes doctors were hesitant to prescribe anti-clotting medication in these patients, because those medications do carry risks, and they perceived this condition as less serious,” says Dr. Cannon. That risk-benefit calculation has changed now amid mounting evidence that MINOCAs often lead to future heart events.

However, that’s not to say that every individual with a MINOCA should be treated with a one-size-fits-all approach, says Dr. Cannon. Individual risk factors should still be considered carefully along with the risks of various treatment options.

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